Each year in the United States 12,000 new cases of thyroid cancer are reported. Recently, somatic gene defects associated with the various human thyroid tumor phenotypes have been identified. However, the prevalence of these gene defects is low, suggesting that many oncogenic events are still to be identified. Gene amplification of oncogenes is a common mechanism of tumorigenesis. Comparative genomic hybridization (CGH) was used to determine chromosomal loci which are amplified in thyroid neoplasms. A discrete amplified locus on 2p21 has been mapped to a BAC clone which will be used to isolate candidate oncogenes. The size of the amplicon will be determined with contigs to this BAC. Exon trapping or other positional cloning strategies will be used to identify coding sequences from within this BAC and its contigs demonstrated to be part of the amplicon. These sequences will then be used to identify the corresponding cDNA from thyroid cDNA libraries. The cDNA will then be examined for expression in normal and tumor thyroid samples by probing a large panel of northern blots. Thyroid as well as other tumors will be examined for structural defects in this sequence. Finally, the possible function of these putative oncogenes will be studied using strategies that will be dictated in part by their sequence.